Sources of Electricity

While most of us are familiar possibly with several sources of
electrical energy, we do not always stop to think of the many
possible sources which are little known, especially to the layman.
We have endeavored in the present article, and with the aid of the
accompanying full page illustration, to describe the principal
known sources of electricity.

Static Electricity: This form of
electricity is that which we see when we stroke pussy's fur in a
dark room and obtain a spark when the hand is withdrawn from
contact with the fur; or again, we may obtain the same form of
electric shock or discharge by rubbing together two dissimilar
substances, such as a stick of sealing wax with a silk
handkerchief, after which it will be found that the electrified
stick of sealing wax will attract bits of paper or small pith
balls. A rapidly moving belt often develops a considerable amount
of static or frictional electricity, which will tend to discharge
to earth whenever possible. One may often stand near such a belt,
and by holding the knuckles or even the ends of the fingers near
the belt, a heavy static discharge will take place between the belt
and the fingers, the electric charge passing thru the body to
earth.

One of the usual and practical sources of such electricity is the
static machine (Fig. 1) and when the handle of such a machine is
turned, one or more insulating discs are rapidly rotated, and by
successive intensification of a very slight electric charge
existing on the tin-foil sectors of these plates before the machine
is started up, a surprisingly powerful static discharge is rapidly
built up. This will manliest itself in the form of an electric
spark, which crashes across the gap between two metal balls on the
side of the machine. There are many other sources of static
electricity but the whole phenomenon is practically the same.

Contact Electricity: It was Volta who
showed that the contact of two dissimilar metals in the air produce
opposite kinds of electrification, one becoming positively, and the
other negatively electrified. There has been considerable
discussion as to the exact action occuring in the production of
electrical currents by the contact of two dissimilar methods in
air, and for a long time, says Silvanus P. Thompson, the existence
of this electrification by contact was denied, or rather it was
declared to be due (when occurring in voltaic combinations) to
chemical actions going on ; whereas, the real truth is that the
electricity of contact and the chemical action are both due to
transfers of electrons between the substances under the peculiar
actions of forces, about which very little is known with certainty
as yet.

Volta found that the difference of electric potential between the
different pairs of metals was not all equal, as while zinc and lead
were respectively positive and negative to a slight degree : zinc
and silver proved to be positive and negative to a much greater
degree. The voltage obtained by the contact between zinc and carbon
is 1.09 volts.

The phenomena of electrical currents produced by the contact of
dissimilar methods is illustrated by Fig. 2. A difference of
potential or voltage is also produced by the contact of two
dissimilar liquids. It has been found that a liquid and a metal in
contact exhibit a difference of potential or voltage, and if the
metal tends to dissolve into the liquid chemical. there will be an
electro-motive force acting from the metal toward the liquid. A hot
metal placed in contact with a cold piece of the same metal, also
produces a difference of potential, and lastly Sir Joseph J.
Thomson has demonstrated that the surface of contact between two
non-conducting substances, such as sealing wax and glass, is the
seat of a permanent difference of potential.

Galvanic Electricity: The primary battery
is generally defined as one in which electrical energy is produced
by chemical means, without having to charge the battery from dynamo
or other source originally. The simplest form of such a battery
comprises a glass or other vessel containing sulfuric acid and
water, or any other oxidizing acid solution, and in which are
immersed two clean metal strips, one of zinc and one of copper.
Most of us are probably familiar with the common form of primary
battery used in American practice for ringing bells and operating
medical coils in the form of the well-known dry cell, or with the
zinc-copper-salammoniac cell. In the zinc-copper-acid cell above
mentioned, a continuous flow of electricity may take place thru a
wire or apparatus which connects the two plates. When such a
current passes, the zinc strip may be seen to waste away, or
decompose by the electro-chemical action taking place, and its
consumption, in fact, furnishes the energy required to drive the
current thru the cell and the connecting wire or apparatus. In such
a cell, the zinc strip forms the positive electrode or negative
terminal, while the copper strip forms the negative electrode or
positive terminal. Such a cell gives about one volt potential.

Fig. 3 shows a unique form of primary battery known as the Hauck
Circulation; battery. In this battery, composed of several cells,
the electrolyte or solution is caused to pass from a tank above the
battery cells, thence thru the first or higher cell, then thru the
next lower container, etc This is a chromic acid battery with
carbon and zinc electrodes. The zincs are located in the
rectangular porous cups while the two carbon plates are outside of
the porous cups, all the space between porous cup and carbon
plates, as well as between the carbon plates and glass vessel being
filled out with small carbon pieces. In the porous cup there is a
sulfuric acid electrolyte, while the carbons stand in chromic acid.
As the latter is caused to circulate continuously- from one battery
to the next, all polarisation is done away with and we obtain a
very steady and powerful current. The battery illustrated gives 6
volts and 60 amperes and can be used to charge storage batteries,
run fans, or electric lamps. It is one of the best chromic acid
batteries ever designed.

Electricity from Gases: Fig. 4 shows the
famous Grove Gas Battery invented in 1J59. It shows how two gases
are used to produce an electric current. The two glass tubes
contain platinum strips coated with spongy- platinum. The glass
bottle contains acidulated water in which the two glass tubes
plunge, as seen. One of the tubes contains oxygen, the other
hydrogen, as will be noted the gases make contact with the
acidulated water. If we connect the two terminals with a
galvanometer we will observe an electric current, the oxygen
furnishing the positive, the hydrogen the negative pole of the
battery. Incidently we note that, as we consume current, the liquid
rises in the two glass tubes, but twice as fast in the hydrogen
tube as in the one containing the oxygen. .As each tube is
identical with the other, except for the gases, it follows that the
current can be due only to the gases. Also different gases produce
different voltages and currents.

Pyro-Electricity or Electricity from
Crystals: In the accompanying Fig. 5, we have several
methods by which minute quantities of electricity are produced from
crystals, when these are manipulated in a specific manner. Certain
crystals, when they are heated or cooled, exhibit electrical
charges at certain regions or poles, and such crystals which become
electrified by heating or cooling are said to be pyro-electric. One
of the principal crystals which manifest this peculiar action is
tourmaline. The tourmaline has been cited in history, and is
mentioned by Theophrastus and Pliny under the name of Lapis
Lyncurius The tourmaline possesses the power of polarizing light,
and is usually found in slightly irregular three-sided prisms
which, when perfect, are pointed at both ends. It is interesting to
note that in heating such a crystal as the tourmaline, it attracts
light pith balls to its ends when electrified. If the temperature
is kept steady, then no such electrical effects are observed either
at high or low temperatures, and again the phenomenon ceases
altogether if the crystal is warmed above ISO" C. If a heated
crystal of tourmaline is suspended by a silk fiber, it will be
attracted and repelled by electrified bodies or by a second heated
tourmaline, Among other crystals which belong in the pyro-electric
family are silicate of zinc, boracite, cane sugar, quartz, tartrate
of potash and sulfate of quinine.

Electricity is produced by the disruption and cleavage of certain
substances as for instance, when a sheet of mica is split apart,
which action is usually accompanied by the production of a number
of sparks, and both laminae are found to be electrified. If sulfur
is fused in a glass dish and allowed to cool, it becomes powerfully
electrified, which action may be tested by lifting out the
crystalline mass with a glass rod. Chocolate is another substance
which manifests such an electrification while becoming solidified.

Piezo-Electricity is the term given to that form of electrical
energy produced when certain crystals are placed under pressure in
a certain direction. With respect to the make-up of the crystal, it
was found that if a crystal of calspar was prest between the
fingers so as to compress it along the blunt edges of the crystal,
that it becomes electrified, and retains its electrical charge for
some days. This phenomenon is believed to be due in certain
crystals to what is known technically as skew-symmetry or hemihedry
in their molecular structure.

Thermo-Electricity: If we take two metal
bars, one cf bismuth and one of antimony, and join these together,
it will be found that an electric current is produced of an
appreciable magnitude when the juncture between the metals is
heated in the flame of a candle or other source of heat. To
demonstrate that there is an electric current produced in all such
cases, it is but necessary to connect a sensitive electric
current-detecting device, such as a galvanometer to the free ends
of the bismuth- antimony couple, as it is called. If all parts of
the circuit, including all sections of the bismuth-antimony couple.
are at one temperature, there will be no current produced, since
the electro-motive forces are in perfect equilibrium. However, when
a junction between two such metals is heated, this equilibrium of
the electrons and molecules no longer exists, and gives way to the
production of an E.M.F. or difference of potential.

As might be suspected, the voltage produced by heating a single
metallic couple, such as the above, is very small, and where a
greater potential is desired a large number of similar couples are
mounted in as compact a manner as possible, and all of the
junctions are heated simultaneously by gas or coal as shown in Fig.
6. The difference of potential for a bismuth-antimony couple is
about 117 microvolts for each degree Centigrade, when the junction
is heated above the rest of the circuit. The total current produced
by the massive compound circular thermopile shown in Fig. 6 is 80
volts and 3 amperes, which is sufficient to light a number of
incandescent lamps.

Dynamic Electricity: The most successful
and practical source of electrical energy as we know it today is
the Dynamo. One of these machines, which depends upon the cutting
of magnetic lines of force by a rotating wire or inductor as it is
called, is shown in Fig. 7. It was Faraday, who early in the 19tli
century discovered that if a circular copper disc be rotated
between the poles of a strong steel magnet or an electro-magnet,
that there would be a current produced, or rather induced in the
moving copper disc, due to the cutting of magnetic lines of force.
The current was found to flow from the shaft supporting the disc to
the rim, or vice versa, according to the direction of rotation.
This current was conducted away by wires, having sliding brush
contacts, one of which was made to bear against the shaft, while
the other made contact with the edge of the disc.

It was not long before the simple copper disc gave way to the more
modern armature, which contains a large number of insulated copper
wires and all of which coils, in consequence, are caused to rotate
rapidly in the powerful field of an electromagnet. These rotating
coils are properly connected to a series of metal bars, assembled
in ring form and known as a commutator, against which contact
brushes bear, leading the current from the armature to the electric
apparatus, such as lamps, motors, etc. The dynamo is always to be
driven by some external prime mover, such as a steam engine, water
wheel, etc. In the dynamo we have the conversion of mechanical
energy into electrical energy.

Electricity From Coal: One of the most
successful forms of apparatus for producing electricity direct from
coal is shown in Fig. 8. This particular type of coal-electric cell
is due to W. W. Jacques. Here we have a carbon cylinder immersed in
a fused caustic soda bath; this is placed in an iron vessel which
also serves as the other electrode of the cell. An air pump is
employed to blow a stream of air thru the caustic soda by means of
a perforated drum under the carbon rod. By means of the coal
furnace the whole cell is maintained at a temperature of 400°C. The
air stream has the effect of causing the carbon to oxidize to CO2,
which mostly bubbles up thru the caustic soda solution and escapes.
This cell gives about 1 volt E.M.F. The action occurring in the
production of electrical energy is believed to be partly voltaic
and thermo-electric. The cell has an efficiency of about 8 per
cent—compared to 12 to 15 per cent for modern steam boiler and
engine plants, and the cost of raw materials to replenish it is
said to be at least 34 times that for a good steam engine, while
the residue or ash from such a battery would possibly weigh 12
times that from a corresponding steam plant.

Plant Electricity: It is not generally
known that certain plants exhibit pronounced electrical activity,
but such is the case. Perhaps the strongest, that is in the sense
of electrical vibrations, is the sensitive plant (Mimosa pud tea),
shown in the illustration (Fig. 9). Others, such as iris,
nicotiana, nasturtiums and practically all the meat-eating plants,
such as the "Venus fly-trap" and the "sundew," afford splendid
examples for experimentation. If any of these be placed "in
connection with a galvanometer by means of electrodes attached to
leaves on different sides, and one side of the plant be exposed to
sunlight while the other side is kept shaded, then within from
three to ten seconds after exposure to sunlight there will be a
flow of electricity from the lighted to the shaded parts amounting
to .005 to .02 volt. This continues for about five minutes, when
the magnet begins to swing back and shows an opposite current of
considerable magnitude. The manifestations are similar to those of
"teranized nerve."

A better understanding of the electrical qualities of plants will,
no doubt, explain many of the hitherto mysterious habits of
meat-eating plants. Especially will this be true of such terrible
and uncanny plant monsters as the "devil's snare" of South America
and the mammoth Utricularia, or fishing plant, which lures minnows
and small animals into its voracious mouth, and suddenly, as if an
electric button were secretly prest, closes in upon its helpless
prey. In other words, it fishes with a net electrically wired!
Strange as it may sound this plant safeguarded itself by means of
its electrical currents ages before we used the electric burglar
alarm and door bell. Were it not for this protection, the plant
could not live and hold its own in such an aurial-infested region
as it needs for its fishing ground.

Animal Electricity: Altho not so commonly
known, there are in the world several varieties of electric fishes
and eels which possess, quite remarkable power. Several species of
these creatures inhabiting the waters of certain parts of the earth
possess the power of producing more or less powerful electric
discharges. Physiologically, the principal creatures of this class
are the Torpedo, the Gymnotus and the Silurus. One of the most
powerful electric fishes is the Raia Torpedo or Electric Ray, of
which there are three species inhabiting the Mediterranean and
Atlantic. This particular specimen is provided with an electric
organ on the back of its head. The organ consists of laminae
composed of polygonal cells to the number of eight hundred or one
thousand, or even more, which is supplied with four large bundle of
nerve fibers. The under surface of this fish is negative: while the
upper surface is positive. With the Gymnotus or Surinam eel, the
electric organ extends the whole length of the body from tail to
head. It has been recorded by Humboldt that a lively combat ensued
between a number of electric eels and a herd of wild horses, which
were driven by the natives unconsciously into the swamps inhabited
by the Gymnotus. This particular specimen of electric fish is said
to be able to give a most terrible shock, and proves a most
formidable antagonist when it has grown to its full length of five
to six feet. In the Silurus shown in our Fig. 10, the electric
current Hows from head to tail.

It has been shown by several scientists that nerve excitations and
muscular contractions of human beings are the seat of slight
electrical currents. For one thing it has been shown that the
beating of the heart really creates rhythmical electro-motive
force.

Photo-Electricity: One of the most
interesting sources of electrical energy and also one of the most
direct methods of production of electro-motive forces is found in
the photo-electric cell. Simply explained this remarkable device
comprises nothing more than two copper plates, one of which is
perforated and blackened by oxidizing in a gas flame, while the
rear or second plate is polished, and both of which plates are
placed in a suitable tank containing a salt-water solution. One
side of the tank which contains the copper plates is lifted with a
glass window and when sunlight, or any other source of light, is
allowed to strike the cell, there is a difference of electric
potential set up between the front and rear copper plates. This
particular cell as developed by Mr. Theodore W. Case, was described
extensively in an article which appeared in the September, 1916,
number of this journal. It was found possible with some of these
photo-electric cells to obtain a voltage of one-tenth and an
amperage of two-tenths ; the cell delivering a steady current as
long as the light shown on it. It is of course possible to connect
a large number of cells in series or parallel to obtain any voltage
or current desired.

Radium Electricity: It is generally
conceded in scientific circles that the activity possest by radium
is fundamentally electrical in nature. Radium gives off three kinds
of rays known as the alpha, beta and gamma rays. It is possible to
influence two of these rays (alpha and beta rays) by means of a
magnet or an electro-magnetic field, which indicates that they are
undoubtedly electrical in their fundamental structure. Another
experiment, which any schoolboy can readily perform with a piece of
radio-active mineral, is as follows: First, an electric charge is
produced on a sensitive gold leaf electroscope, so that the leaves
diverge; then grasp a piece of the radioactive mineral (some may be
so fortunate as to possess a tube containing a small quantity of
radium bromid and bring this into proximity with the metal ball or
disc at the top of a charged electroscope. It will be noted that
the latter loses its charge on the gold leaves almost instantly;
the electronic activity of the radium bromid or other radio-active
substance used creating a change in the electrical field about the
electroscope, apparently making it more conductive, so that the
bound electric charge on the gold leaves can escape. Those
interested in the subject of "Radium" and the many electrical and
other effects created by the greatest mystery of the scientific
world to-day will do well to read the extensive article on this
subject, which appeared in the September, 1916, number of The
Electrical Experimenter.